Small-scale chemical reactors have many potential applications where compactness, lightweight, and portability are required. One example is in the supply of hydrogen for portable fuel cells where the transport of compressed hydrogen is not practical. Higher energy storage densities are achieved by reforming liquid fuels such as methanol and ethanol to hydrogen and feeding the fuel cell directly. Using this to power electronic devices in the 1-100 W power range such as cell phones and laptop computers clearly demands a simple, small, and low-weight design to compete with current battery technology. Such distributed chemical processing may also be advantageous in processing toxic reagents where it may be safer to produce smaller amounts on site as they are needed rather than producing, transporting, and storing them in large quantities. In addition to compactness and portability, heat and mass transport limitations become less significant at smaller scales, allowing reactions to approach their intrinsic rate and for efficient heat transfer between reactor components.